High temperature resistant acoustical board



N 2 1966 R. F. SHANNON ETAL 3,

HIGH TEMPERATURE RESISTANT ACOUSTICAL BOARD Filed May 24, 1965 INVENTORS P/CHAPD E 5H4A/A/0A/ &

JERRY L 4 T TO RWE 1 5 United States Patent 3,286,785 HIGH TEMPERATURE RESISTANT ACOUSTICAL BOARD Richard F. Shannon, Lancaster, and Jerry L. Helser, He-

bron, Ohio, assignors to Owens-Corning Fiberglas Corporation, a corporation of Delaware Filed May 24, 1965, Ser. No. 457,984 12 Claims. (CL 181-33) The present invention concerns structural, acoustical and thermal insulating boards which are capable of retaining their integrity and dimensional stability at temperatures in excess of 1000 F., and particularly low density siliceousfiber boards possessing an inorganic lamina at one surface and within the voids existing in the fibrous low density structure.

Structural and decorative elements formed from interbonded or intermeshed siliceous fibers, such as glass, mineral Wool or asbestos fibers, have achieved extensive use in applications such as ceiling and wall tiles, panels or boards, in which they provide excellent acoustical and thermal insulating properties. comprise an integral, relatively rigid, mass of fibers grouped into a thin panel-like structure having two major opposed and substantially parallel surfaces, a thickness in the order of one-tenth or less of the major dimension of the structure, and possessing a density in the range of 1 to 30 pounds per cubic foot. Due to the non-compustibility of the siliceous fibers, such structures are also valued for their fire resistance.

However, in recent years public concern has shifted to the fire resistance of the total structure as opposed to the combustibility of its individual elements. It was then found that these non-combustible elements contribute to flame spread or building collapse as the result of this loss of integrity at temperatures experienced during a fire. In the first instance, these non-combustible elements are commonly employed to mask or seal off such readily com bustible elements as wooden studs, joists,.partitions, decking, and the like. At relatively low temperatures, e.g. 500 F., these low density materials perform the desired function in an adequate fashion in both thermally insulating' the combustible materials which they conceal and thereby preventing the transfer of temperatures adequate to initiate combustion, and in physically blocking direct flame transfer. However, at higher temperatures, e.g. 1000" F., and despite their own incombustibility, these elements undergo structural failures which permit the transfer of heat or flame to the combustible elements. Such failures result from the sagging, slumping, warping, shrinking, relamination or complete disintegration of the incombustible boards and the ignition of the combustible elements occurs in one of several manners. For example, the sagging, slumping, warping or shrinking of the elements results in their separation from their fastening or suspension means and the formation of a gap oropening between abutting or adjacent boards. Such apertures permit the transfer of heat and/ or flame capable of igniting combustible materials located behind the incombustible boards. Alternatively, delamination or disintegration provides apertures for heat or flame transfer through the fibrous boards.

In addition, heat or flame transfer through these siliceous fiber boards may also weaken concealed non-combustible structural elements such as steel beams or girders and concrete decks, to cause a partial or total collapse of the building structure.

As a consequence of this discovery many localities have amended building codes to require prolonged resistance to flame and heat transfer at high temperatures, and particularly in public buildings. Insurance rates have also been adjusted in recognition of this hazard since a build- Such elements normally- .Typical of such tests and the resultant standards, are the Underwriters Laboratory fire rating tests in which the thermal-acoustical boards are erected in their usual manner of installation, within a furnace chamber approximat ing the dimensions of a room. Thermocouples are then positioned on the top side of a concrete deck below which is suspended the board to be tested. Flames are then ignited within the chamber and the temperature is progressively elevated, i.e. 1000 F., five minutes after the initiation of the test, 1700 F. at one hour, 1850 F. at 2 hours, etc., to simulate the conditions which would be experienced during an actual fire. The test is terminated whenever any of the thermocouples sense temperatures which would be adequate to ignite combustible building elements or to weaken noncombustible elements such as steel beams or concrete decks. This test yields a fire rat ing based upon the length of endurance of the medium tested under the prescribed conditions. For example, an acoustical board which endured for one hour before per mitting the transfer of temperatures adequate to initiate combustion or cause the collapse of noncombustible elements would receive a one hour rating. A failure is experienced whenever any single thermocouple reaches 325 F., above ambient temperature, or when the average temperature of the thermocouples reaches 250 F., above ambient temperature. This test has been described in detail in order to illustrate the improvements made possible by the inventive materials, in terms of the conditions which must be endured.

Consequently, the present invention is directed to the provision of low density decorative and structural elements formed from siliceous fibers, which exhibit structural integrity and dimensional stalbility at temperatures in excess of 1000' F., while retaining the acoustical and thermal insulating properties for which they are valued.

Another object is the pmovision of methods for the preparation of such low density decorative and structural elements.

A further object is the provision of irnpregnants cap-able of imparting the prescribed integrity to such decorative and structural elements.

Structural integrity, as used herein, is employed to define the ability to resistthe transfer of heat and flames through apertures resulting fnom tJhe delamination or disintegration of the structure, or through apertures resulting from the separation of the low density boards from their fastenings, suspension systems or from albutting, adjacent boards, upon exposure to temperatures in excess of 1000 F. Consequently, the termstructural integrity contains an aspect of dimensional stability in respect to resistance to shrinkage, expansion and warping or sagging. It should also be noted that the acoustical properties of the structures include both sound absorption and resistance to sound transmission. The former is provided by the low density, void-filled region which is retained at one major surface of the board, while the latter is improved by virtue of the formation of a dense zone which is substantially impervious to sound at the opposite major surface. At the same time, the insulating values of the boards are enhanced by virtue of the opacifying effect of the dense layer.

The above objects and their achievement are described in detail in the following specification and the attached drawings in which:

FIGURE 1 is a fragmentary sectional view of a product prepared in accordance with the invention; and,

present in the impregnant.

. 3 FIGURE 2 is a schematic representation of an apparatus suitable for the practice of the methods of the invention.

The foregoing objects are achieved by means of the deposition of a thin, continuous inorganic structural phase, or layer, within the voids present within a resin-bonded, low density fibrous medium and immediately adjacent to one of the two major surfaces of the low density fibrous board. The extent of such deposition is limited and controlled in order to prevent the impregnation of the other or opposite major surface, and to thereby retain the desirable thermal and acoustical properties of the low density medium of which the second major surface is composed.

Specifically, an aqueous slurry containing a specific combination of inorganic ingredients formulated to provide the desired structural integrity and dimensional stability, is applied to one surface of the low density fibrous element and then deposited within the voids present in the fibrous medium and adjacent to the point of application. In determining the nature of a layer adequate to provide the prescribed structural integrity, and of the low density zone of the opposite surface adequate to yield the desired acoustical and thermal insulating properties, it has been found that a structural layer having a thickness of 15 mils is adequate, while the acoustical-thermal low density zone or layer must have .a thickness of at least 50 mils. However, since the low density boards which are treated in accordance with the invention normally have a thickness of at least 375 mils, the structural layer or impregnated zone normally has a thickness of at least 50 mils while an unimpregnated zone having a thickness of at least 125 mils is preferred.

After depositing and positioning the impregnant to the desired depth, the aqueous component is dispelled by drying to leave a strong rigid structural phase or layer.

I. Impregnants.The inventive impregnants contain both inorganic particulate matter, and a binder phase which is capable of interadherring the inorganic particles both at ambient conditions and during exposure t-o temperatures in excess of 1000 F. Specifically, the binder phase contains between 5 to 95% by weight of colloidal silica and between 5 to 95% by weight of bentonite, and comprises between 2 to 25% by weight of the total solids The impregnant contains between 1 to 20% by weight of colloidal silica and between 1 to by weight of bentonite. It should be noted that references to quantities of colloidal silica relate to the quantities of silica solids, although these compositions are normally employed as dispersions in a liquid carrier medium such as water.

The inorganic particles which are intenbonded by the foregoing binder phase include a combination of both materials possessing a'melting point below 2000 F., and materials which melt above that temperature. The lower melting materials are the aluminosilicates of the Group I and II metals, sodium, potassium, calcium, magnesium, and barium, and alnminosilica-tes containing two or more of these metals. The high melting materials comprise certain hydrous aluminum silicates which are subsequently described. This combination is based upon the discovery that the formation of a molten or ceramic phase is highly desirable in the attainment of structural integrity at temperatures experienced during a fire or a fire test;

It is believed that the lower melting materials pro 'vide a new or auxiliary adhesive p'hase upon exposure to temperatures in the range of 1000-25 00 F., which serves to interadhere the higher melting particles and to maintain structural integrity. While structural integrity resulting from a liquid or molten phase may at first appear contradictory, the nature of this liquid must be considered. Specifically, the Group I and/or Group II metals function as fluxes which facilitate the melting of a portion of the ingredients of the impregnant and form an extremely viscous adhesive. compositions commonly possess viscosities in the range of For example, molten glass 10 to 10" poises and consequently are not highly fluid liquids in the ordinary sense of the word. The value of thermally inert particles interbonded by the described liquid adhesive, over thermally inert but structurally weak imprcgnants is aptly demonstrated by the fire ratings achieved with the inventive impregnants.

The previously described binder phase, i.e. bentonite and colloidal silica, is employed to interbond between to 98% by weight of an admixture of low and high melting materials. In turn, this admixture comprises between 10 to by weight of the higher melting hydrated aluminum silicate particles and between 10 to 90% by weight of the lower melting sodium, potassium, calcium, magnesium and barium aluminosilicates. Consequently, the impregnant composition contains between 7.5 to 90% by weight of both the lower and the higher melting materials.

Thus, the impregnants generally comprise:

Percent by weight Preferably the impregnants contain:

Percent by weight Colloidal silica (solids) 2-6 Bentonite 3-5 Ball clay 30-60 Feldspar 30-60 Colloidalsilica and silica sols are commercially available compositions and materials of this nature, as well as methods for their preparation, are disclosed by US. 2,244,325, 3,083,167, 3,041,140 and 3,128,251.

Bentonite is a commonly known clay mineral composed essentially of montmorillonite and beidellite; it is colloidal hydrated aluminum silicate or sodium montmorillonite.

The hydrated aluminum silicates employed by the invention are ball clays consisting primarily of kaolinite, illite and montmorillonite, with minor quantities of ferric oxide, finely divided silica and titanium dioxide, and trace amounts of lime, magnesia, soda, and potash. More precisely, they contain between 50-75% by weight of SiO between 15-35% by weight of A1 0 and between 0.5- 10% by weight of Fe O with conventional silica, alumina and iron contents of approximately 57:27:1. Ball clays are distinguished from the more common clays such as kaolin clays, by their lower alumina contents, e.g. 15- 35% as opposed to 37-50% for kaolin clays. In addition, between 50-90% of the particles which make up the ball clays employed by the invention have a diameter of 10 microns or less. Furthermore, and as contrasted with the subsequently discussed alkali metal aluminosilicates, the ball clays have a total alkali and alkaline earth metal content of between 0.5-4% by weight. It should be noted that in references made to the quantity of ingredients present in clays or minerals, the total weight of the composition from which the percentages are derived may contain minor quantities of organic materials. Typical of these hydrated aluminum silicates are the Maryland and Tennessee ball clays generally, and such specific materials as Saxon clay, Yankee ball clay, Rex clay, XB ball clay, pyrophyllite, and the like.

The lower melting material is preferably feldspar but one may generally employ the Group I and II metal aluminosilicates of sodium, potassium, calcium, magnesium or barium aluminosilicates, combinations thereof, or aluminosilicates which containtwo or more of the specified metal ions, i.e. Na, K, Ca, Ba or Mg. In addition, these metals are present in a quantity of between 6-20% by weight, and preferably 8-15% by weight.

I Examples of such aluminosilicates include the feldspars such as orthoclase, albite, hydrophane, microcline,

anorthite, anorthoclase, etc.; and such "compounds as This may be employed to the rate and depth of impreg nepheline, cancrinite, thomsonite, eucryptite, grossularite, nation. However, the impregnation depth and rate may alumontite, phillipsite, etc. In addition, the majority of also be controlled by means independent of the impregthe particles making up these compositions also have nant. For example, vacuum or mechanically pressurized diameters of no more than microns. 5 impregnation, e.g. a doctor blade, may be employed to The examples in the following table provide a number force a highly viscous impregnant to the desired depth of formulations suitable forum in the present invention, within the fibrous substrate. Alternatively, the fibrous in which the quantities of ingredients are expressed as substrate may be pre-treated with a wetting agent, e.g. percentages by weight: sprayed with a solution of an organosilicone fluid, to fa- TABLE 1 Examples Ingredients 1 i 2 t a l 4 l 5 6 7 s 9 FeldsparI 47 73.3 13 36.75 76 Feldspar II 7O Feldspar III. Nepheline.

Ball clay I Ball clay II.

Ball clay III Colloidal silica (solids) 2.7 5.1 3 3 10 1.7 5 Bentonite 3 .3 3 .3 5 5 5 5 3 3 .3 8

Feldspar I in the above table comprised the following cilitate and control the rate and depth of impregnation by quantities of ingredients expressed in percentages by viscous slurries. Similarly, the wetting agent may be inweight; corporated in the impregnant. The siliceous fibers which make up the low density boards treated in accordance 67.53 36 with the invention, frequently contain a water repellant 19. 1 8 2 5 3 which causes the board to resist wetting and penetration g K20 1 by the aqueous slurries which are employed. In such Organic"- cases, the board should be either pre-treated with -a wetting agent, or an agent capable of modifying the surface Its sieve analysis was a residue of 0.3% on a 200 mesh, tension properties of the slurry should be incorporated in and 3.2% on a 325 mesh (68.2% of the particles posthe slurry. A wetting agent which has proved highly satsessed a diameter of 20 microns or less). Feldspars II isfactory for the above purposes is sodium dioctyl sulfoand III were similar in respect to ingredients and total Succinate having a molecular weight of 444 and available alkali and alkaline earth metal content, i.e. approximately from American Cyanamid under the tradename A o ol 12-16% by weight, but feldspar II possessed a higher T- K O and lower Na O content, while feldspar III con- It should be noted that all of the impregnants of the tained a-higher CaO and MgO content. above examples were applied to siliceous fiber acoustical n clays I and 11 i h above bk Contained th boards and subjected to a simulated fire test to yield fire following quantities of ingredients and possessed the speciratings in the Iahge of hours- These ratings p fied properties: sent a substantial improvement over untreated boards which yield a rating of approximately 1545 minutes, or

Ban Clay I Ban Clay H boards treated or impregnated with clays, silica, alumina,

and the like, which normally provide a one hour rating.

60. 19 58% It should also be noted that various other ingredients 28.3; 23.58 such as reinforcements, opacifiers, fillers, wetting agents,

: anti-foaming agents, and the like, may be added to the 3.21 g. lnventive impregnants. Typical of such additives are,

: 3 asbestos, asbestine, wollastonite, titania, zircon, zirconia,

organic 8.2g 5.3g alumina, carbon black, crystalline silica, calcium car'- I 1 bonate, barlum sulfate, magnesium carbon-ate, ferric sulon absorption (percent) a4. 5 fate, sodium hexametaphosphate, and the like,

3535 5 gfgg g ggggg gg It must also be realized that the inventive combinations crons or less (pe rcent) 81.0 93.0 of higher and lower melting materials may be simulated shnnkage 2900 R (percent) by adding fiuxing agents to hydrated aluminum silicates having a'high melting point, e. 2000-3500 F. For Ball clay III was similar to ball clay I with the exception example, a fl i agent such sodium Oxide may be that a portion of the aluminum silicate was present as dd d t a b ll l i a it adequate to exert a pyrophyllite. fluxing effect upon only a portion of the clay, e.g. 8% by The colloidal silica of the foregoing examp s were weight. Such an expedient also results in a molten or p y as aqueous dispersions Containing between ceramic adhesive phase but is more expensive and diffi- 60% by weight of colloidal silica and preferably 40% cult to prepare, since minerals which naturally contain a by weight. H w v t q i ie t d r f r to the fluxing agent content, e.g. feldspar, are readily available. amount of silica solids employed. II. lmpregnlated products.As previously mentioned,

The impregnants of the above examples were prepared the products of the invention comprise an acoustical panel, by admixing the ingredients with water to form a slurry. board, or tile formed from siliceous fibers bonded or en- While a slurry containing 2070%, and preferably 50% tangled into a mass having a density in the range of l by Weight f Water 18 preferred in most Cases, the ratio 0 to 30 p.c.f., and possessing two substantially parallel mamust be gauged to yield an impregnant of the viscosity jor surfaces, one of which is impregnated with the invendesired for the specific applicator system and substrate tive compositions. The resultant product retains its deemployed. For example, in the case of low density fisirable acoustical and thermal insulating values while brous substrates, the viscosity of the impregnant is noryielding highly improved structural integrity, and resistmally increased by increasing the percentage of solids. ance to heat or flame transfer when exposed to high temperatures. In order to preserve the acoustical absorption properties of the board, the impregnation of the board throughout its entire thickness, i.e. the filling of all of the voids present in the board, must obviously be avoided. However, satisfactory acoustical properties, and some degree of thermal insulation, are realized when a low density region having a depth of no more than 50 mils is left upon the unimpregnated surface of the board. In turn, an impregnated region having a thickness of no more than mils is adequate to provide structural integrity which permits the board to endure temperatures as high .as 2500 F., without failing. It should be realized that in the case of thicker boards, the temperatures which are experienced by the impregnant are lower as the result of the layer of low density thermal insulation which is present at the outside between the impregnant and the heat source.

The acoustical boards comprising glass fibers have an apparent density of from 1 to 30 pounds per cubic foot and are \from 250 to 3000 mils thick. These boards impregnated to a depth of at least 15 mils with the treating material.

Preferred embodiments of the invention comprise fibrous glass boards having a density in the range of 8 to 15 p.c.f., a thickness of from 350 to 1500 mils, and an impregnated region having a thickness of about 50 to; 750 mils and generally about 50 to 200 mils. Normally, the uni-mpregnated zone will comprise approximately one-half of the thickness of the board. Examples of such structures comprise a one inch thick board with an impregnated zone or structural layer having a thickness of 50 mils and a 78 inch thick board having an impregnated zone having a thickness of 500 mils. In the case of boards having a density in the range of 9 to 13 pounds per cubic foot and a thickness of no more than one inch, impregn-ants constituting between 0.3 to 0.8 pounds per square foot of the impregnated board have proved generally satisfact-ory. Similarly, a preferred product comprises a board having a density in the range of 9-13 p.c.f., a thickness of between 350 to 1500 mils, and containing between 0.3 and 0.8 pounds of the impregnant present in each square foot of the impregnated board. However, as previously noted, boards having densities of between 1 to 30 p.c.f., and a thickness as great as 3 inches, have been prepared and have yielded the desired properties.

A product prepared in accordance with the invention is depicted by FIGURE 1 which provides a fragmentary, sectional view through a fibrous board prepared in accordance with the invention. As may be seen, one surface 11 of the low density, fibrous board 12 has been impregnated to yield a dense layer 13 which serves as a structural member. As also may be observed, the dense layer 13 also contains the fibers 14 of which the board 12 is composed, and which provide an additional benefit in reinforcing the dense layer 13. In turn, a low density unimpregnated phase 15 is left intact at the opposite surface 16 of the board 12 to provide the desired thermal and acoustical properties.

It should be noted that in the illustrated products the structural value of the dense layer 13 functions primarily after the fibers of the low density unimpregnated phase 15 have been weakened, softened or melted and following pyrolysis of the resin binder. At such time, the dense layer 13 becomes the primary or sole supporting, spanning, or suspending means and may provide the sole source of structural integrity for the board 12.

As previously mentioned, in the use of the inventive impregnants, i.e. containing Group I or II metal aluminosilicate, it is believed that the dense layer 13 does not remain inert upon exposure to temperatures in the range of 1500 F. or higher. Specifically, when inorganic impregnants resistant to temperatures as high as 3000 F. were employed as the dense layer 13, the structures still failed at temperatures far below the melting points of the impregnants. It is believed that such failures were the result of the absence of an adequate binder phase within the impregnants. In essence, the inert impregnants suffered from thermal erosion or the like, lost integrity, and failed. It was found that the use of the inventive binder phase, i.e. benton-ite and colloidal silica, overcame this inadequacy. It was further found that the presence of an ingredient which became molten upon exposure to temperatures in the range of 1500 -2500 F., actually improved the integrity of the structure when it was exposed to those temperatures.

The low density fibrous boards employed as the substrate utilized in the above examples and impregnated in the practice of the invention are typified by those disclosed by US. 2,790,741; 2,791,289; 2,882,764; 2,984,312; 3,082,- 143; 3,111,188; 3,118,516; 3,159,235; and similar structures employing glass, mineral wool or asbestos fibers.

In addition, the binder employed to bond the siliceous fibers together intoa low density mass, e.g. phenol-formaldehyde or melamine resins, may also contain a fire retardant additive such as clay, asbestine, etc. Alternatively, the fibrous board may be first washed, but not thoroughly impregnated, i.e. without filling the voids throughout the thickness of the board and destroying insulating and acoustical values, with an inorganic material such as a clay slurry, etc. Such measures improve the total fire resistance of the structure although failing to provide adequate structural integrity at high temperatures.

III. Preparation 07 the impregnated structures-As previously mentioned, the impregnated structures are prepared by depositing a slurry of the inventive impregnant upon one surface of the fibrous board, introducing the impregnant within the voids present upon one surface of the porous board without filling the voids present upon the opposite surface of the board, and drying the impregnant.

A method for fabricating these products is depicted by FIGURE 2 which shows a schematic representation of apparatus suitable for the impregnation of low density siliceous fiber substrates. As shown, fibrous boards 21 are carried by means of a foraminous conveyor belt 22 beneath a trough 23 which dispenses an impregnating slurry 24 upon the upper surface 25 of the boards 21. The deposited impregnant 226 is then passed beneath a metering knife blade 27 which controls the thickness and consequently the quantity of the deposited impregnant 26. The boards 21 are then passed beneath and in contact with a pressure roll 28 which forces the deposited impregnant within the upper surface of the boards 21. To facilitate and control the depth of penetration of the boards 21 by the impregnant, the boards 21 and rforaminous conveyor belt 22 may then be passed over a suction box 29 which serves to draw the impregnant within the boards 21 and may implement or replace the effect of the pressure roll 28. Alternatively, or in conjunction with the foregoing process, a sprinkler 30 may deposit a wetting agent such as a silicone fluid upon the upper surface 25 of the boards 21 prior to the deposition of the impregnant. The use of such a wetting agent facilitates the rapidity and extent of the penetration of the boards 21 by the impregnant. The drying of the impregnant may be accomplished by conventional oven treatments. For example, boards having a density of approximately p.c.f., .a thickness of between 350 to 1000 mils, and containing an impregnant layer weighing approximately 0.8 pounds (aqueous slurry, 50% solids) per square foot of the board, may be oven dried at a temperature of 400 F., in approximately one hour.

Obviously, the primary sources of control for both the rapidity and the degree of impregnation reside in the matching of the viscosity and/or surface tension of the impregnant in relation to the density of the board, the slurry may be merely metered and evenly deposited upon the upper surface of the board, and will immediately 9 flow to a desired depth within the upper surface of the board, without penetrating to the opposite surface.

In the impregnation of a fibrous glass board having a density of 9-13 p.c.f., it is preferred to employ a slurry having a viscosity of approximately 100-200 centipoises. In such case, the slurry flows entirely within the board to a depth of approximately 125-180 mils within a matter of 1 to 3 seconds.

While the majority of the specification has concerned glass fibers, it must be realized that boards of a comparable density prepared from other siliceous fibers, e.g. mineral wool, asbestos, etc., are equally benefited by the practices of the invention, and yield products which simultaneously provide thermal and acoustical insulating values and prolonged structural integrity at temperatures in excess of 1000 F. I

It is obvious that the present invention provides fire resistant, structural integrity imparting impregnants; acoustical and thermal insulating structural elements capable of retaining their integrity at high temperatures; and methods for the preparation of the foregoing structural elements.

The treating materials of this invention can also be used for bonding aggregates such as vermiculite, perlite, glass foam pellets, glass beads and the like to produce products such as high temperature resistant pipe insulation. Likewise these treating compositions can be used for near total impregnation coup-led with one or more b ack-coatings to provide novel effects. The coatings can be used for steel and wood decks to provide improved fire ratings.

It is further apparent that various alterations and substit-utions may be made in the com-positions, products and methods without departing from the spirit of the invention as defined by the following claims.

We claim:

1. An acoustical and thermal insulating element capable of maintaining structural integrity at temperatures in excess of 1000 F., comprising a plurality of siliceous fibers interbonded into an integral, void-containing mass having a density of between 1 to 30 pounds per cubic foot and shaped in the form of a panel having two substantially parallel major surface and a thickness of between 250 and 3000 mils, and deposited within said voids present between said fibers and adjacent to one of said surfaces and to a depth of at least 15 mils, an impregnant comprising between 75 to 98% by weight of aluminum silicate particles consisting essentially of between to 90% by weight of hydrated aluminum silicate containing between 50 to 75% by weight of SiO and between to 35% by weight of A1 0 and between 10 to 90% by weight of an aluminosilicate of a metal selected from the group consisting of sodium, potassium, calcium, magnesium, barium and combinations of said metals, in which said metal is present in a quantity in excess of 6% by weight, and admixed with and interadhering said alluminum silicate particles between 2 to by weight of a binder phase consisting essentially of between 1 to 20% by weight of colloidal silica and between 1 to 15% by weight of bentonite, the remainder of said panel and the portion of said panel immediately adjacent to the second of said major surfaces to a depth of at least 50 mils being substantially devoid of said impregnant and retaining said density of 1 to pounds per cubic foot.

2. An acoustical and thermal insulating element as claimed by claim 1 in which said siliceous fibers are glass fibers.

3. An acoustical and thermal insulating element as claimed by claim 1 in which said aluminosilicate of a metal is feldspar.

4. An acoustical and thermal insulating element capable of maintaing structural integrity at temperatures in excess of 1000 F., comprising a plurality of glass fibers interbonded into an integral void-containing mass having a density of between 8 to 15 pounds per cubic foot and shaped in the form of a panel having two substantially parallel major surfaces and a thickness of between 350 to 1500 mils, and deposited within said voids present between said fibers and adjacent to one of said surfaces and to a depth of at least 15 mils, an impregnant comprising between 75 to 98% by weight of aluminum silicate particles and consisting essentially of between 10 to by weight of hydrated aluminum silicate containing between 50 to 75% by weight of SiO and between 15 to 35% by weight of A1 0 and between 10 to 90% by weight of an aluminosilicate of a metal selected from the group consisting of sodium, potassium, calcium, mag nesium, barium and combinations of said metals, in which said metal is present in a quantity in excess of 6% by weight, and admixed with and interadhering said aluminum silicate particles between 2 to 25 by weight of a binder phase consisting essentially of between 1 to 2 0% by weight of colloidal silica and between 1 to 15% by weight of bentonite, the remainder of said panel and the portion of said panel immediately adjacent to the second of said major surfaces to a depth of at least 50 mils being substantially devoid of said impregnant and retaining said density of .8 to 15 pounds per cubic foot.

5. A method for the preparation of acoustical and thermal insulating elements capable of maintaining struc tural integrity at temperatures in excess of 1000 F., comprising applying to one major surface of a panel comprising a plurality of siliceous fibers interbonded into an integral void-containing mass having a density of between 1 to 30 pounds per cubic foot and having two substantially parallel major surfaces and a thickness of between 250 to 3000 mils, an aqueous dispersion of an impregnant comprising between 75 to 98% by Weight of aluminium silicate particles and consisting essentially of between 10 to 90% by weight of hydrated aluminum silicate containing between 50 to 75 by weight of SiO and between 15 to 35% by weight of A1 0 and between 10 to 90% by weight of an aluminosilicate of a metal selected from the group consisting of sodium, potassium, calcium, magnesium, barium and combinations of said metals, in which said metal is present in a quantity in excess of 6% by weight, and between 2 to 25% by weight of a binder phase consisting essentially of between 1 to 20% by weight of colloidal silica and between 1 to 15% by weight of bentonite, depositing said dispersion within the voids present between said fibers adjacent to said one major surface and to a depth of at least 15 mils from said one major surface, maintaining the remainder of said panel and the portion of said panel adjacent to the second of said major surfaces to a depth of at least 50 mils from said second major surface substantially devoid of said aqueous slurry, and drying said panel to remove the aqueous phase of said dispersion.

6. A method as claimed by claim 5 in which suction is applied to said second major surface subsequent to the application of said aqueous dispersion to said one major surface.

7. A method as claimed by claim 5 in which said impregnant is displaced from said one major surface to said voids adjacent to said one major surface by applying mechanical pressure to said aqueous dispersion.

8. A method as claimed by claim 5 in which said siliceous fibers are glass fibers.

9. A method as claimed by claim 5 in which said one surface is treated with a wetting agent prior to said applying of said aqueous dispresion.

10. A method as claimed by claim 5 in which said aqueous dispersion also contains a wetting agent.

11. A method for the preparation of acoustical and thermal insulating elements capable of maintaining structural integrity at temperatures in excess of 1000 F., comprising applying to one major surface of a panel comprising a plurality of glass fibers interbonded into an integral void-containing mass having a density of between 8 to 15 pounds per cubic foot and having two substantially parallel major surfaces and a thickness of between 350" to 1500 mills, an aqueous dispersion of an impregnant comprising between 75 to 98% by weight of aluminum silicate particles and consisting essentially of between 10 to 90% by weight of hydrated aluminum silicate containing between 50 and 75% by weight of Si and between 15 to 35% by weight of A1 0 and between to 90% by weight of an aluminosilicate of a metal selected from the group consisting of sodium, potassium, calcium, magnesium, barium and combinations of said metals, in which said metal is present in a quantity in excess of 6% by weight, and between 2 to 25% by weight of a binder phase consisting essentially of between 1 to 20% by weight of colloidal silica and between 1 to by weight of bentonite, said fibers adjacent to said one major surface and to a depth of at least 15 mils from said one major surface, maintaining the remainder of said panel and the portion of said panel adjacent to the second of said major surfaces to a depth of at least 50 mils from said second major sunface substantially devoid of said aqueous slurry, and drying said panel to remove the aqueous phase of said dispersion.

12. A heat resistant, integrity-imparting impregnant consisting essentially of an aqueous dispersion of between 2 to by weight of a binder phase consisting essentially of between 1 to 20% by weight of colloidal silica and between 1 to 15% by Weight of bentonite, andbetween to 98% by weight of aluminum silicate particles consisting essentially of between 10 to by weight of hydrated aluminum silicate containing between 5 0 to 75 by weight of SiO and between 15 to 35% by weight of A1 0 and between 10 to 90% by weight of an aluminosilicate of a metal selected from the group consisting of sodium, potassium, calcium, magnesium, barium and combinations of these, in which said metal is present in a quantity in excess of 6% by weight.

References Cited by the Examiner UNITED STATES PATENTS 3,017,318 1/1962 Labino et a1. 117-126 3,077,413 2/1963 Campbell 117-126 3,141,809 7/1964 DiMaio et a1. 181-33 FOREIGN PATENTS 822,261 10/1959 Great Britain.

RICHARD B. WILKINSON, Primary Examiner. 

1. AN ACOUSTICAL AND THERMAL INSULATING ELEMENT CAPABLE OF MAINTAING STRUCTURAL INTEGRITY AT TEMPERATURES IN EXCESS OF 10000*F. COMPRISING A PLURALITY OF SILECEOUS FIBERS INTERBONDED INTO AN INTEGRAL, VOID-CONTAINING MASS HAVING A SENSITY OF BETWEEN 1 TO 30 POUNDS PER CUBIC FOOT AND SHAPED IN THE FORM OF A PANEL HAVING TWO SUBSTANTIALLY PARALLEL MAJOR SURFACE AND A THICKNESS OF BETWEEN 250 AND 30000 MILS, AND DEPOSITED WITHIN SAID VOIDS PRESENT BETWEEN SAID FIBERS AND ADJACENT TO ONE OF SAID SURFACES AND TO A DEPTH OF AT LEAST 15 MILS, AND IMPREGNANT COMPRISING BETWEEN 75 TO 98% BY WEIGHT OF ALUMINUM SILICATE PARTICLES CONSISTING ESSENTIALLY OF BETWWEEN 10 TO 90% BY WEIGHT OF HYDRATED ALUMINUM SILICATE CONTAINING BETWEEN 50 TO 755 BY WEIGHT OF SIO2 AND BETWEEN 15 TO 35% BY WEIGHT OF A12O3, AND BETWEEN 10 TO 90% BY WEIGHT OF AN ALUMINOSILICATE OF A METAL SELECTED FROM THE GROUP CONSISTING OF SODIUM, POTASSIUM, CALCIUM, MAGNESIUM, BARIUM AND COMBINATIONS OF SAID METALS, IN WHICH 